An algal bloom is an explosion of growth and population of algae, which typically consist of one or a small number of phytoplankton, the foundation of the food chain. These blooms occur all over the world, even in the icy waters of the Arctic Ocean. They normally occur for a reason such as an overabundance of nutrients in the water from natural or man-made sources, or naturally with rising spring temperatures. In the Arctic, higher temperatures and melting ice have caused a shift in the region's natural bloom cycle. They are progressively coming earlier, and the shift has great importance to the entire food chain and carbon cycling.

ADVERTISEMENT

Researchers from Scripps Institution of Oceanography at UC San Diego, together with colleagues from Portugal and Mexico, have studied the yearly spring phytoplankton bloom in the Arctic. Their research indicates the peak timing of the event has been coming earlier in the year over the past decade.

To arrive at this conclusion, they used satellite images to see changes in the ocean color. Algal blooms normally cause a greening of the ocean by the sheer abundance of their numbers. Newer satellites are even able to directly detect the production of phytoplankton. The data showed that the annual spring bloom has arrived up to 50 days earlier in certain areas. Most of the areas with earlier blooms are also areas where ice cover has diminished, creating gaps where blooms may be possible.

The blooms typically last between one and two weeks. They create a major addition to organic matter which then benefits the entire ecosystem from bottom to top. Also, like any plant, algae requires carbon dioxide for growth. They are a major part of the global carbon cycle, converting carbon dioxide into organic material.

However, earlier blooms may not sync up with the natural cycles of marine species which depend on them. For example, the peak of the bloom may occur while the creatures are still in their egg or larval life stages, and the organic matter produced may not be useable to them. The resulting mismatch in timing may explain the annual variability of fish stocks in the region.

"The spring bloom provides a major source of food for zooplankton, fish and bottom-dwelling animals," says Mati Kahru, lead author of the study. "The advancement of the bloom time may have consequences for the Arctic ecosystem." The concern for the researchers is that earlier blooms may spread to other parts of the globe and throw off marine ecosystems elsewhere. Food chains around the world could be affected.